Getting the right exposure for digital printing (digital capture)

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FrameMakers

FrameMakers

PFG, Picture Framing God
Joined
Mar 20, 2001
Posts
7,395
Loc
Powell, OH
We are getting in more and more print jobs for artists.

For smaller stuff we have used our scanner and stitched sections together. While this works fine for smaller items it is not practical for jobs over 16x20 and even then has its limitations.

I have been working on a digital capture set-up using my Canon 40D and a sliding platform for the artwork. I shoot small segments of the art and then slide the image from left to right 4-6" each time. I can then lower the image and shoot another row. These will all be stitched together in Photoshop to produce a high quality image.

I have a X-Rite Colorchecker Passport to get the white balance and colors correct. With this system, you shoot in Raw format and apply the changes in Adobe Camera Raw (ACR) before opening them in Photoshop.

My issue right now is getting the exposure correct so that it matches the artwork. Since Raw images capture a larger amount of information there really is no set exposure.

When dealing with a photograph, we can set the exposures to what pleases us with an eye toward not clipping detail. When trying to reproduce art, we are trying to match a painting even if we could make the copy more dynamic.

Is there a way in ACR or PS to nail down the exposure without making a series of test prints and wasting a ton of paper or canvas?

I know there are other methods for digital capture but at this point I can't afford a betterlight system or a cruise scanner.
 
Dave,

I do a lot of Art documentation; no stitching, though, and I use the LCD and eyeball it for exposure compensation. For stitching, a consistent exposure, i.e. setting it and using manual, would seem more important, especially when shooting raw. That and getting the WB right. I use Kodak color strips when color is critical, and a custom WB set off of a gray card.

How big are you printing? Do you need the stitched image?
 
there is a slight flaw with your setup

if you move the artwork, the light on the piece is changed, therefore it wont look right generally

better to move the camera

there is a set exposure in a raw file, and those settings are passed to your raw processor, but then there is some latitude in both directions

BUT, it actually sounds like your not using the camera in manual mode, but one of the more auto modes, maybe apreture priority or something

and that maybe your only using natural light. if your only using natural light you have an issue when shooting multiple shots as the light can change between shots etc, therefore matching the pieces could be an issue


i would suggest some kind of artifical light, maybe a set of the contiuous low enegery kits around could work, but you will need to diffuse them etc, and make sure they are the main light and not the natural light still coming into the room
 
Yeah, first you need to tell us how you are lighting your shots.

Then you need to make sure your lighting is the same all over the section you are shooting. A couple of points difference isn't that bad but 15 or more and you will have a difference in the edges of the sections of the art in lighting value and it will show. If your lights aren't set properly, you will have a hot spot somewhere and less around the edges and the corners are usually the least lit.

There is a piece of software out there called Equalight that will measure a white board that you shoot in the exact pixel size as the piece you are shooting. You shoot the sections and then shoot the white board without moving anything..getting the exact same size as each section. Then the software reads the white file and finds the brightest pixel and brings all the other pixels up to match so the board is lit evenly.
Then it applies that algorithim to the files of the sections and brings them up so they are evenly lit. Great little piece of software.
Here's the link to the site:

http://store.rmimaging.com/equalight.aspx

I use a movable wall to shoot my large stuff and really big lights and still will have falloff of the light in certain areas of the art and the Equalight software solves that problem every time.
 
Bron, the painting I am currently working with is 20x40 but she also has others that are much larger.
I am getting a reading in aperture priority mode then using that in full manual mode so that the camera does not try to interpret each section independently.

stcstc, I disagree about moving the camera. By controlling the light over the section that I am shooting (about 8"x12") when I move the art, the light in this section is exactly the same, as the lights don't move. It is also much easier to have an even light without fall off in such a small area than it would be on the entire painting.

With that said, the lighting is probably the biggest area that improvement could be made in. I am currently using 4 clamp lights with full spectrum incandescent bulbs. They are currently not diffused but are set back 6' from the subject. The clamp lights are set on 2 vertical supports 45° from the wall. I also have florescent lights on in the shop that I could turn off. There is a little natural light, but this really is minimal.

The results that I am getting are quite good, but I am striving for better. I can adjust the settings to get what I am after, just was looking for something to get me there more quickly and consistently. Kind of like what a gray card does when using it in PS levels with the eyedropper tool.
 
the reason i am saying about moving the image

for example, if its an oil, it has depth, ie its not flat

as you move the image within the lighting, the depth, because of the angle of the lights will change

a bit like how your shadow moves through the day

this means the interaction between the edges of the sections will be different

your much better putting the camera on a track with the focal plane of the camera completley paralell to the piece and be able to then move the camera
 
Framah, I liked your set-up and developed my own based on a lot of your ideas.

Just a bit more info. I am shooting with a Canon 40D in full manual mode. The lens I am using is a Canon EF 70-200mm f/2.8L IS lens at about 80mm. With this lens I can keep the camera back far enough to stay out of the lights path and have no noticeable lens distortion along the edges. I am also firing the camera remotely so I don't have any camera shake.

I just got a Manfrotto 410 junior geared tripod head. This is so much better then the ball head I had before.
 
IMAG1905.jpg


This does not show the lighting. It was shot with my cell phone since it shows my 40D :)

The target is the size of the sections I am shooting.
 
Dave,
How big are you trying to print? Most of the stuff I shoot is for computer or web use, and when for publication, it's still pretty small, so one image is all I need. Just wondering if you need the stitched image?

I use florescent bulbs (30W, 5500K, from Adorama) in reflector holders with shoot through umbrellas to diffuse, and polarizing gels and filter if needed. I was just on location and was able to use natural daylight, even though I had all the lighting gear with me. Whatever works.

I use the self timer to fire the camera.
 
Bron, I will be printing these full sized on my Epson 9900 44" printer.
 
Wanna buy some studio lights?? Since I bought my pair of Northlights, I don't need the Bowens fluorescent lights I have.

I have a pair of 200w and a pair of 400w. Go to B&H's website and check them out. Search for Bowens SL455 and Bowens SL855.
I'll take 25% less than their price plus shipping.
Looks like you have a good start on the shooting studio!!:thumbsup:
 
I also find I only need to overlap the section by about 25-30%.
Also... Dibond makes a good rigid white board to shoot.

Here's my latest shot of the studio with the new lights and my new computer and monitor.

 
Dang, those new lights look nice. A bit out of my price range though. Do you do enough of this kind of work to justify the expense that you have put into it?

So far, I have under $100 in everything other then the camera and tripod.
 
I'm starting to get in enough work that I feel it was worth it to set myself up to be able to shoot anything that comes in.
I quickly realized that the setup I started with was too small for the bigger stuff that was coming in.
Yeah, it is a medium sized bucket load of money but as of now, i'm the only one who can shoot pretty much anything and then print it the same size. I have even had the local offset printer here refer one of their customers to me as they couldn't get the colors right. This type of expansion in a business will take a few years to support itself and for now the framing is the sugar daddy.
The other nice (for me) thing is the only other guy who shoots art is getting out of it due to an illness he is beginning to experience. I figure soon, he will be sending people to me when he quits.

Plus, I now have my studio to play in when I'm not going crazy in the store.:shutup:
 
Sorry Framah, your lights even at 75% of retail are out of my budget for this project. I did just order a couple of softboxes from Amazon.
 
FrameMakers said:
Is there a way in ACR or PS to nail down the exposure without making a series of test prints and wasting a ton of paper or canvas?

I know there are other methods for digital capture but at this point I can't afford a betterlight system or a cruise scanner.
Click to expand...

Dave,

You might get more consistency if you do not make the color and tone adjustments in RAW, but pull the raw files into PS without any adjustment. Stitch & blend them. Then apply a curve and using the white color picker on the white part of the calibration card. This should yield more consistency and get you very close to the correct color. May need to fine-tune the color with another curve.

Perhaps selecting the white point in RAW is creating slight variations in each segment of your image. Cummulatively, the may cause more variation, which the blend has to consider.

BTW, I use Novatron lighting with homemade diffusers and polarizers on the lights, and of course the polarizer on the camera. Also using a Canon 5D with 100mm macro lens. I check the setup on large images by using a light meter over various parts of the target image and adjust the polarizer on the camera to remove specular highlights. I have several 36"x48" canvas images in the gallery to photograph and they will be captured as one shot in raw mode.
 
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